I am using Flickr API in my webapp and I want to display my photo gallery to the visitors using C# and Asp.net. I am able to display images but every time it asks for login to user. Now my question is that how can I skip this login part as I cannot expect visitor to have a Flickr/Yahoo account?
You can use the Flickr API to view public photos without login. You need to set the visibility of your photos to public.
Only photos visible to the calling user will ever be returned. To return private or semi-private photos, the caller must be authenticated and logged in with 'read' permissions, and have permission to view the photos. So if you want to show public photos, you don't need user login. You only need to do auth with your app key and call the API method to retrieve the photos.
This tutorial gives you an idea how to call without login. It's for JQuery but shows how the call is made.